Fluorescence sensing based on phenylenediacetonitrile doped into polymer host

Solution-processible phenylenediacetonitrile compounds featuring reduced and extended conjugation backbone were investigated for application in fluorescence sensing. Utilization of phenylenediacetonitrile-doped polymer films (at the concentration of 5 wt%) prepared by the simple spin-coating method was demonstrated to have a potential in sensing of volatile organic vapor as well as elevated temperatures, i.e., those exceeding glass transition temperature of the polymer. The sensing by the solution-processed films was accomplished via the distinct change in emission color (from blue to green) followed by emission intensity enhancement. The sensing mechanism was found to rely on diffusion-induced crystalline aggregate formation as proved by optical and atomic force microscopies as well as optical spectroscopy. The compound with the reduced conjugation demonstrated the superiority over the extended-backbone compound imposing greater twisted geometry, which along with dihexyl-type of side-groups facilitated the assembly of the molecules into ordered (crystalline) nanoaggregates as confirmed by polarized optical microscopy. A minute-time response to THF vapor or thermal stimulus implied potential for phenylenediacetonitrile doped into polymer host in fluorescence sensing application.